The goal of the proposed effort is to develop a biosensor for rapid, on-site measurement of chemical environmental contaminants. The crux of the innovation is to use grating-coupled surface plasmon resonance (GCSPR) transduction in conjunction with a microarray transducer chip and an imaging CCD detector to implement a system capable of highly multiplexed detection of many analytes with high sensitivity in a small portable, rugged, low-cost package suitable for field use by minimally trained personnel. The proposed device will solve two of the most important shortcomings of present technology for field environmental analysis; namely, the limitation of current systems to the detection of a single analyte or a single class of closely related compounds, and the limited sensitivity and accuracy of field assays. In addition, we expect that the proposed system will materially increase the ease and speed with which these assays can be performed in the field. The objectives of the Phase I effort are to build a breadboard prototype of a GCSPR imaging system to assess its feasibility for multiplexed detection, and to demonstrate the operation of the system with a prototype assay using polycyclic aromatic hydrocarbons (PAH) as an analyte model system. Potential applications include environmental testing, clinical diagnostics, homeland defense applications and the life sciences research market.